Nitric oxide represses inhibitory kappaB kinase through S-nitrosylation

Obesity and mitochondrial uncoupling - an opportunity for the carbon monoxide-based pharmacology of metabolic diseases

Obesity, a chronic and progressive disease with a complex etiology, remains a significant global health challenge. Despite advancements in lifestyle interventions, pharmacological therapies, and bariatric surgery, substantial barriers to effective and sustained obesity management persist. Resistance to weight loss and gradual weight regain are commonly reported, limiting the long-term success of both non-pharmacological and pharmacological strategies. A possible contributor is metabolic adaptation, a phenomenon characterized by reduced metabolic rate and energy expenditure following weight loss, which hinders therapeutic efficacy. To address these challenges, increasing attention has been directed toward strategies that counteract maladaptive mechanisms by modulating metabolic rate and enhancing energy expenditure. One promising approach involves mitochondrial uncoupling, where electron transport and oxygen consumption are disconnected from ATP synthesis, promoting energy dissipation. Preclinical studies have demonstrated the potential of various chemical compounds with uncoupling activity as anti-obesity agents. Additionally, carbon monoxide (CO) has emerged as a significant gaseous signaling molecule in human physiology, with anti-inflammatory, antioxidative, and cytoprotective properties. Advances in CO-based pharmacology have led to the development of controlled-release CO donors, enabling precise therapeutic application. Experimental studies suggest that CO modulates mitochondrial bioenergetics, induces mild mitochondrial uncoupling, and regulates mitochondrial biogenesis. By integrating these findings, this review uniquely connects scientific threads, offering a comprehensive synthesis of current knowledge while proposing innovative directions in mitochondrial, metabolic and CO-based pharmacological research. It highlights the potential of CO-based pharmacology to regulate metabolic rate, support weight loss, and address obesity-related dysfunctions, thus suggesting novel pathways for advancing obesity treatment.

S-nitrosylation of EZH2 alters PRC2 assembly, methyltransferase activity, and EZH2 stability to maintain endothelial homeostasis

Nitric oxide (NO), a versatile bio-active molecule modulates cellular functions through diverse mechanisms including S-nitrosylation of proteins. Herein, we report S-nitrosylation of selected cysteine residues of EZH2 in endothelial cells, which interplays with its stability and functions. We detect a significant reduction in H3K27me3 upon S-nitrosylation of EZH2 as contributed by the early dissociation of SUZ12 from the PRC2. Moreover, S-nitrosylation of EZH2 causes its cytosolic translocation, ubiquitination, and degradation. Further analysis reveal S-nitrosylation of cysteine 329 induces EZH2 instability, whereas S-nitrosylation of cysteine 700 abrogates its catalytic activity. We further show that S-nitrosylation-dependent regulation of EZH2 maintains endothelial homeostasis in both physiological and pathological settings. Molecular dynamics simulation reveals the inability of SUZ12 to efficiently bind to the SAL domain of EZH2 upon S-nitrosylation. Taken together, our study reports S-nitrosylation-dependent regulation of EZH2 and its associated PRC2 complex, thereby influencing the epigenetics of endothelial homeostasis.

Acute COVID-19 and LongCOVID syndrome - molecular implications for therapeutic strategies - review

Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) has been recognized not only for its acute effects but also for its ability to cause LongCOVID Syndrome (LCS), a condition characterized by persistent symptoms affecting multiple organ systems. This review examines the molecular and immunological mechanisms underlying LCS, with a particular focus on autophagy inhibition, chronic inflammation, oxidative, nitrosative and calcium stress, viral persistence and autoimmunology. Potential pathophysiological mechanisms involved in LCS include (1) autoimmune activation, (2) latent viral persistence, where SARS-CoV-2 continues to influence host metabolism, (3) reactivation of latent pathogens such as Epstein-Barr virus (EBV) or cytomegalovirus (CMV), exacerbating immune and metabolic dysregulation, and (4) possible persistent metabolic and inflammatory dysregulation, where the body fails to restore post-infection homeostasis. The manipulation of cellular pathways by SARS-CoV-2 proteins is a critical aspect of the virus' ability to evade immune clearance and establish long-term dysfunction. Viral proteins such as NSP13, ORF3a and ORF8 have been shown to disrupt autophagy, thereby impairing viral clearance and promoting immune evasion. In addition, mitochondrial dysfunction, dysregulated calcium signaling, oxidative stress, chronic HIF-1α activation and Nrf2 inhibition create a self-sustaining inflammatory feedback loop that contributes to tissue damage and persistent symptoms. Therefore understanding the molecular basis of LCS is critical for the development of effective therapeutic strategies. Targeting autophagy and Nrf2 activation, glycolysis inhibition, and restoration calcium homeostasis may provide novel strategies to mitigate the long-term consequences of SARS-CoV-2 infection. Future research should focus on personalized therapeutic interventions based on the dominant molecular perturbations in individual patients.

Understanding chronic inflammation: couplings between cytokines, ROS, NO, Cai 2+, HIF-1α, Nrf2 and autophagy

Chronic inflammation is an important component of many diseases, including autoimmune diseases, intracellular infections, dysbiosis and degenerative diseases. An important element of this state is the mainly positive feedback between inflammatory cytokines, reactive oxygen species (ROS), nitric oxide (NO), increased intracellular calcium, hypoxia-inducible factor 1-alpha (HIF-1α) stabilisation and mitochondrial oxidative stress, which, under normal conditions, enhance the response against pathogens. Autophagy and the nuclear factor erythroid 2-related factor 2 (Nrf2)-mediated antioxidant response are mainly negatively coupled with the above-mentioned elements to maintain the defence response at a level appropriate to the severity of the infection. The current review is the first attempt to build a multidimensional model of cellular self-regulation of chronic inflammation. It describes the feedbacks involved in the inflammatory response and explains the possible pathways by which inflammation becomes chronic. The multiplicity of positive feedbacks suggests that symptomatic treatment of chronic inflammation should focus on inhibiting multiple positive feedbacks to effectively suppress all dysregulated elements including inflammation, oxidative stress, calcium stress, mito-stress and other metabolic disturbances.

Redox signaling in the pancreas in health and disease

This review addresses oxidative stress and redox signaling in the pancreas under healthy physiological conditions as well as in acute pancreatitis, chronic pancreatitis, pancreatic cancer, and diabetes. Physiological redox homeodynamics is maintained mainly by NRF2/KEAP1, NF-κB, protein tyrosine phosphatases, peroxisome proliferator-activated receptor-γ coactivator 1α (PGC1α), and normal autophagy. Depletion of reduced glutathione (GSH) in the pancreas is a hallmark of acute pancreatitis and is initially accompanied by disulfide stress, which is characterized by protein cysteinylation without increased glutathione oxidation. A cross talk between oxidative stress, MAPKs, and NF-κB amplifies the inflammatory cascade, with PP2A and PGC1α as key redox regulatory nodes. In acute pancreatitis, nitration of cystathionine-β synthase causes blockade of the transsulfuration pathway leading to increased homocysteine levels, whereas p53 triggers necroptosis in the pancreas through downregulation of sulfiredoxin, PGC1α, and peroxiredoxin 3. Chronic pancreatitis exhibits oxidative distress mediated by NADPH oxidase 1 and/or CYP2E1, which promotes cell death, fibrosis, and inflammation. Oxidative stress cooperates with mutant KRAS to initiate and promote pancreatic adenocarcinoma. Mutant KRAS increases mitochondrial reactive oxygen species (ROS), which trigger acinar-to-ductal metaplasia and progression to pancreatic intraepithelial neoplasia (PanIN). ROS are maintained at a sufficient level to promote cell proliferation, while avoiding cell death or senescence through formation of NADPH and GSH and activation of NRF2, HIF-1/2α, and CREB. Redox signaling also plays a fundamental role in differentiation, proliferation, and insulin secretion of β-cells. However, ROS overproduction promotes β-cell dysfunction and apoptosis in type 1 and type 2 diabetes.

Systematic analysis of the global characteristics and reciprocal effects of S-nitrosylation and S-persulfidation in the human proteome

Gasotransmitter-mediated cysteine post-translational modifications, including S-nitrosylation (SNO) and S-persulfidation (SSH), play crucial roles and interact in various biological processes. However, there has been a delay in appreciating the interactional rules between SNO and SSH. Here, all human S-nitrosylated and S-persulfidated proteomic data were curated, and comprehensive analyses from multiple perspectives, including sequence, structure, function, and exact protein impacts (e.g., up-/down-regulation), were performed. Although these two modifications collectively regulated a wide array of proteins to jointly maintain redox homeostasis, they also exhibited intriguing differences. First, SNO tended to be more accessible and functionally clustered in pathways associated with cell damage repair and other protein modifications, such as phosphorylation and ubiquitination. Second, SSH preferentially targeted cysteines in disulfide bonds and modulated tissue development and immune-related pathways. Finally, regardless of whether SNO and SSH occupied the same position of a given protein, their combined effect tended to be suppressive when acting synergistically; otherwise, SNO likely inhibited while SSH activated the target protein. Indeed, a side-by-side comparison of SNO and SSH shed light on their globally reciprocal effects and provided a reference for further research on gasotransmitter-mediated biological effects.

Endothelial Reactive Oxygen Species: Key Players in Cardiovascular Health and Disease

Significance: Endothelial cells (ECs) line the entire vasculature system and serve as both barriers and facilitators of intra- and interorgan communication. Positioned to rapidly sense internal and external stressors, ECs dynamically adjust their functionality. Endothelial dysfunction occurs when the ability of ECs to react to stressors is impaired, which precedes many cardiovascular diseases (CVDs). While EC reactive oxygen species (ROS) have historically been implicated as mediators of endothelial dysfunction, more recent studies highlight the central role of ROS in physiological endothelial signaling. Recent Advances: New evidence has uncovered that EC ROS are fundamental in determining how ECs interact with their environment and respond to stress. EC ROS levels are mediated by external factors such as diet and pathogens, as well as inherent characteristics, including sex and location. Changes in EC ROS impact EC function, leading to changes in metabolism, cell communication, and potentially disrupted signaling in CVDs. Critical Issues: Current endothelial biology concepts integrate the dual nature of ROS, emphasizing the importance of EC ROS in physiological stress adaptation and their contribution to CVDs. Understanding the discrete, localized signaling of EC ROS will be critical in preventing adverse cardiovascular outcomes. Future Directions: Exploring how the EC ROS environment alters EC function and cross-cellular communication is critical. Considering the inherent heterogeneity among EC populations and understanding how EC ROS contribute to this diversity and the role of sexual dimorphism in the EC ROS environment will be fundamental for developing new effective cardiovascular treatment strategies.

Redox signaling and skeletal muscle adaptation during aerobic exercise

Redox regulation is a fundamental physiological phenomenon related to oxygen-dependent metabolism, and skeletal muscle is mainly regarded as a primary site for oxidative phosphorylation. Several studies have revealed the importance of reactive oxygen and nitrogen species (RONS) in the signaling process relating to muscle adaptation during exercise. To date, improving knowledge of redox signaling in modulating exercise adaptation has been the subject of comprehensive work and scientific inquiry. The primary aim of this review is to elucidate the molecular and biochemical pathways aligned to RONS as activators of skeletal muscle adaptation and to further identify the interconnecting mechanisms controlling redox balance. We also discuss the RONS-mediated pathways during the muscle adaptive process, including mitochondrial biogenesis, muscle remodeling, vascular angiogenesis, neuron regeneration, and the role of exogenous antioxidants.

Mechanism of non-thermal atmospheric plasma in anti-tumor: influencing intracellular RONS and regulating signaling pathways

Non-thermal atmospheric plasma (NTAP) has been proven to be an effective anti-tumor tool, with various biological effects such as inhibiting tumor proliferation, metastasis, and promoting tumor cell apoptosis. At present, the main conclusion is that ROS and RNS are the main effector components of NTAP, but the mechanisms of which still lack systematic summary. Therefore, in this review, we first summarized the mechanism by which NTAP directly or indirectly causes an increase in intracellular RONS concentration, and the multiple pathways dysregulation (i.e. NRF2, PI3K, MAPK, NF-κB) induced by intracellular RONS. Then, we generalized the relationship between NTAP induced pathways dysregulation and the various biological effects it brought. The summary of the anti-tumor mechanism of NTAP is helpful for its further research and clinical transformation.

S-nitrosoglutathione reductase-dependent p65 denitrosation promotes osteoclastogenesis by facilitating recruitment of p65 to NFATc1 promoter

Osteoclasts, the exclusive bone resorptive cells, are indispensable for bone remodeling. Hence, understanding novel signaling modulators regulating osteoclastogenesis is clinically important. Nuclear factor of activated T-cells, cytoplasmic 1 (NFATc1) is a master transcription factor in osteoclastogenesis, and binding of NF-κB p65 subunit to NFATc1 promoter is required for its expression. It is well-established that DNA binding activity of p65 can be regulated by various post-translational modifications, including S-nitrosation. Recent studies have demonstrated that S-nitrosoglutathione reductase (GSNOR)-mediated protein denitrosation participated in cell fate commitment by regulating gene transcription. However, the role of GSNOR in osteoclastogenesis remains unexplored and enigmatic. Here, we investigated the effect of GSNOR-mediated denitrosation of p65 on osteoclastogenesis. Our results revealed that GSNOR was up-regulated during osteoclastogenesis in vitro. Moreover, GSNOR inhibition with a chemical inhibitor impaired osteoclast differentiation, podosome belt formation, and bone resorption activity. Furthermore, GSNOR inhibition enhanced the S-nitrosation level of p65, precluded the binding of p65 to NFATc1 promoter, and suppressed NFATc1 expression. In addition, mouse model of lipopolysaccharides (LPS)-induced calvarial osteolysis was employed to evaluate the therapeutic effect of GSNOR inhibitor in vivo. Our results indicated that GSNOR inhibitor treatment alleviated the inflammatory bone loss by impairing osteoclast formation in mice. Taken together, these data have shown that GSNOR activity is required for osteoclastogenesis by facilitating binding of p65 to NFATc1 promoter via promoting p65 denitrosation, suggesting that GSNOR may be a potential therapeutic target in the treatment of osteolytic diseases.

Reactive gliosis in traumatic brain injury: a comprehensive review

Traumatic brain injury (TBI) is one of the most common pathological conditions impacting the central nervous system (CNS). A neurological deficit associated with TBI results from a complex of pathogenetic mechanisms including glutamate excitotoxicity, inflammation, demyelination, programmed cell death, or the development of edema. The critical components contributing to CNS response, damage control, and regeneration after TBI are glial cells-in reaction to tissue damage, their activation, hypertrophy, and proliferation occur, followed by the formation of a glial scar. The glial scar creates a barrier in damaged tissue and helps protect the CNS in the acute phase post-injury. However, this process prevents complete tissue recovery in the late/chronic phase by producing permanent scarring, which significantly impacts brain function. Various glial cell types participate in the scar formation, but this process is mostly attributed to reactive astrocytes and microglia, which play important roles in several brain pathologies. Novel technologies including whole-genome transcriptomic and epigenomic analyses, and unbiased proteomics, show that both astrocytes and microglia represent groups of heterogenic cell subpopulations with different genomic and functional characteristics, that are responsible for their role in neurodegeneration, neuroprotection and regeneration. Depending on the representation of distinct glia subpopulations, the tissue damage as well as the regenerative processes or delayed neurodegeneration after TBI may thus differ in nearby or remote areas or in different brain structures. This review summarizes TBI as a complex process, where the resultant effect is severity-, region- and time-dependent and determined by the model of the CNS injury and the distance of the explored area from the lesion site. Here, we also discuss findings concerning intercellular signaling, long-term impacts of TBI and the possibilities of novel therapeutical approaches. We believe that a comprehensive study with an emphasis on glial cells, involved in tissue post-injury processes, may be helpful for further research of TBI and be the decisive factor when choosing a TBI model.

Biopterin metabolism and nitric oxide recoupling in cancer

Tetrahydrobiopterin is a cofactor necessary for the activity of several enzymes, the most studied of which is nitric oxide synthase. The role of this cofactor-enzyme relationship in vascular biology is well established. Recently, tetrahydrobiopterin metabolism has received increasing attention in the field of cancer immunology and immunotherapy due to its involvement in the cytotoxic T cell response. Past research has demonstrated that when the availability of BH4 is low, as it is in chronic inflammatory conditions and tumors, electron transfer in the active site of nitric oxide synthase becomes uncoupled from the oxidation of arginine. This results in the production of radical species that are capable of a direct attack on tetrahydrobiopterin, further depleting its local availability. This feedforward loop may act like a molecular switch, reinforcing low tetrahydrobiopterin levels leading to altered NO signaling, restrained immune effector activity, and perpetual vascular inflammation within the tumor microenvironment. In this review, we discuss the evidence for this underappreciated mechanism in different aspects of tumor progression and therapeutic responses. Furthermore, we discuss the preclinical evidence supporting a clinical role for tetrahydrobiopterin supplementation to enhance immunotherapy and radiotherapy for solid tumors and the potential safety concerns.

"NO" Time in Fear Response: Possible Implication of Nitric-Oxide-Related Mechanisms in PTSD

Post-traumatic stress disorder (PTSD) is a psychiatric condition characterized by persistent fear responses and altered neurotransmitter functioning due to traumatic experiences. Stress predominantly affects glutamate, a neurotransmitter crucial for synaptic plasticity and memory formation. Activation of the N-Methyl-D-Aspartate glutamate receptors (NMDAR) can trigger the formation of a complex comprising postsynaptic density protein-95 (PSD95), the neuronal nitric oxide synthase (nNOS), and its adaptor protein (NOS1AP). This complex is pivotal in activating nNOS and nitric oxide (NO) production, which, in turn, activates downstream pathways that modulate neuronal signaling, including synaptic plasticity/transmission, inflammation, and cell death. The involvement of nNOS and NOS1AP in the susceptibility of PTSD and its comorbidities has been widely shown. Therefore, understanding the interplay between stress, fear, and NO is essential for comprehending the maintenance and progression of PTSD, since NO is involved in fear acquisition and extinction processes. Moreover, NO induces post-translational modifications (PTMs), including S-nitrosylation and nitration, which alter protein function and structure for intracellular signaling. Although evidence suggests that NO influences synaptic plasticity and memory processing, the specific role of PTMs in the pathophysiology of PTSD remains unclear. This review highlights pathways modulated by NO that could be relevant to stress and PTSD.

Efficacies of S-nitrosoglutathione (GSNO) and GSNO reductase inhibitor in SARS-CoV-2 spike protein induced acute lung disease in mice

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which initially surfaced in late 2019, often triggers severe pulmonary complications, encompassing various disease mechanisms such as intense lung inflammation, vascular dysfunction, and pulmonary embolism. Currently, however, there's no drug addressing all these mechanisms simultaneously. This study explored the multi-targeting potential of S-nitrosoglutathione (GSNO) and N6022, an inhibitor of GSNO reductase (GSNOR) on markers of inflammatory, vascular, and thrombotic diseases related to COVID-19-induced acute lung disease. For this, acute lung disease was induced in C57BL/6 mice through intranasal administration of recombinant SARS-CoV-2 spike protein S1 domain (SP-S1). The mice exhibited fever, body weight loss, and increased blood levels and lung expression of proinflammatory cytokines (e.g., TNF-α and IL-6) as well as increased vascular inflammation mediated by ICAM-1 and VCAM-1 and lung infiltration by immune cells (e.g., neutrophils, monocytes, and activated cytotoxic and helper T cells). Further, the mice exhibited increased lung hyperpermeability (lung Evans blue extravasation) leading to lung edema development as well as elevated blood coagulation factors (e.g., fibrinogen, thrombin, activated platelets, and von Willebrand factor) and lung fibrin deposition. Similar to the patients with COVID-19, male mice showed more severe disease than female mice, along with higher GSNOR expression in the lungs. Optimization of GSNO by treatment with exogenous GSNO or inhibition of GSNOR by N6022 (or GSNO knockout) protects against SP-S1-induced lung diseases in both genders. These findings provide evidence for the potential efficacies of GSNO and GSNOR inhibitors in addressing the multi-mechanistic nature of SARS-CoV-2 SP-associated acute-lung disease.

The Potential Role of Nitric Oxide as a Therapeutic Agent against SARS-CoV-2 Infection

The global coronavirus disease 2019 (COVID-19) pandemic caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has become the greatest worldwide public health threat of this century, which may predispose multi-organ failure (especially the lung) and death despite numerous mild and moderate symptoms. Recent studies have unraveled the molecular and clinical characteristics of the infectivity, pathogenicity, and immune evasion of SARS-CoV-2 and thus improved the development of many different therapeutic strategies to combat COVID-19, including treatment and prevention. Previous studies have indicated that nitric oxide (NO) is an antimicrobial and anti-inflammatory molecule with key roles in pulmonary vascular function in the context of viral infections and other pulmonary disease states. This review summarized the recent advances of the pathogenesis of SARS-CoV-2, and accordingly elaborated on the potential application of NO in the management of patients with COVID-19 through antiviral activities and anti-inflammatory properties, which mitigate the propagation of this disease. Although there are some limits of NO in the treatment of COVID-19, it might be a worthy candidate in the multiple stages of COVID-19 prevention or therapy.

Targeting Transcription Factor YY1 for Cancer Treatment: Current Strategies and Future Directions

Cancer represents a significant and persistent global health burden, with its impact underscored by its prevalence and devastating consequences. Whereas numerous oncogenes could contribute to cancer development, a group of transcription factors (TFs) are overactive in the majority of tumors. Targeting these TFs may also combat the downstream oncogenes activated by the TFs, making them attractive potential targets for effective antitumor therapeutic strategy. One such TF is yin yang 1 (YY1), which plays crucial roles in the development and progression of various tumors. In preclinical studies, YY1 inhibition has shown efficacy in inhibiting tumor growth, promoting apoptosis, and sensitizing tumor cells to chemotherapy. Recent studies have also revealed the potential of combining YY1 inhibition with immunotherapy for enhanced antitumor effects. However, clinical translation of YY1-targeted therapy still faces challenges in drug specificity and delivery. This review provides an overview of YY1 biology, its role in tumor development and progression, as well as the strategies explored for YY1-targeted therapy, with a focus on their clinical implications, including those using small molecule inhibitors, RNA interference, and gene editing techniques. Finally, we discuss the challenges and current limitations of targeting YY1 and the need for further research in this area.

S-Nitrosylation of Tissue Transglutaminase in Modulating Glycolysis, Oxidative Stress, and Inflammatory Responses in Normal and Indoxyl-Sulfate-Induced Endothelial Cells

Circulating uremic toxin indoxyl sulfate (IS), endothelial cell (EC) dysfunction, and decreased nitric oxide (NO) bioavailability are found in chronic kidney disease patients. NO nitrosylates/denitrosylates a specific protein's cysteine residue(s), forming S-nitrosothios (SNOs), and the decreased NO bioavailability could interfere with NO-mediated signaling events. We were interested in investigating the underlying mechanism(s) of the reduced NO and how it would regulate the S-nitrosylation of tissue transglutaminase (TG2) and its substrates on glycolytic, redox and inflammatory responses in normal and IS-induced EC injury. TG2, a therapeutic target for fibrosis, has a Ca²⁺-dependent transamidase (TGase) that is modulated by S-nitrosylation. We found IS increased oxidative stress, reduced NADPH and GSH levels, and uncoupled eNOS to generate NO. Immunoblot analysis demonstrated the upregulation of an angiotensin-converting enzyme (ACE) and significant downregulation of the beneficial ACE2 isoform that could contribute to oxidative stress in IS-induced injury. An in situ TGase assay demonstrated IS-activated TG2/TGase aminylated eNOS, NFkB, IkBα, PKM2, G6PD, GAPDH, and fibronectin (FN), leading to caspases activation. Except for FN, TGase substrates were all differentially S-nitrosylated either with or without IS but were denitrosylated in the presence of a specific, irreversible TG2/TGase inhibitor ZDON, suggesting ZDON-bound TG2 was not effectively transnitrosylating to TG2/TGase substrates. The data suggest novel roles of TG2 in the aminylation of its substrates and could also potentially function as a Cys-to-Cys S-nitrosylase to exert NO's bioactivity to its substrates and modulate glycolysis, redox, and inflammation in normal and IS-induced EC injury.

The good Samaritan glutathione-S-transferase P1: An evolving relationship in nitric oxide metabolism mediated by the direct interactions between multiple effector molecules

Glutathione-S-transferases (GSTs) are phase II detoxification isozymes that conjugate glutathione (GSH) to xenobiotics and also suppress redox stress. It was suggested that GSTs have evolved not to enhance their GSH affinity, but to better interact with and metabolize cytotoxic nitric oxide (NO). The interactions between NO and GSTs involve their ability to bind and store NO as dinitrosyl-dithiol iron complexes (DNICs) within cells. Additionally, the association of GSTP1 with inducible nitric oxide synthase (iNOS) results in its inhibition. The function of NO in vasodilation together with studies associating GSTM1 or GSTT1 null genotypes with preeclampsia, additionally suggests an intriguing connection between NO and GSTs. Furthermore, suppression of c-Jun N-terminal kinase (JNK) activity occurs upon increased levels of GSTP1 or NO that decreases transcription of JNK target genes such as c-Jun and c-Fos, which inhibit apoptosis. This latter effect is mediated by the direct association of GSTs with MAPK proteins. GSTP1 can also inhibit nuclear factor kappa B (NF-κB) signaling through its interactions with IKKβ and Iκα, resulting in decreased iNOS expression and the stimulation of apoptosis. It can be suggested that the inhibitory activity of GSTP1 within the JNK and NF-κB pathways may be involved in crosstalk between survival and apoptosis pathways and modulating NO-mediated ROS generation. These studies highlight an innovative role of GSTs in NO metabolism through their interaction with multiple effector proteins, with GSTP1 functioning as a "good Samaritan" within each pathway to promote favorable cellular conditions and NO levels.

Recent advances in diverse nanosystems for nitric oxide delivery in cancer therapy

Gas therapy has been proven to be a promising and advantageous treatment option for cancers. Studies have shown that nitric oxide (NO) is one of the smallest structurally significant gas molecules with great potential to suppress cancer. However, there is controversy and concern about its use as it exhibits the opposite physiological effects based on its levels in the tumor. Therefore, the anti-cancer mechanism of NO is the key to cancer treatment, and rationally designed NO delivery systems are crucial to the success of NO biomedical applications. This review summarizes the endogenous production of NO, its physiological mechanisms of action, the application of NO in cancer treatment, and nano-delivery systems for delivering NO donors. Moreover, it briefly reviews challenges in delivering NO from different nanoparticles and the issues associated with its combination treatment strategies. The advantages and challenges of various NO delivery platforms are recapitulated for possible transformation into clinical applications.

Redox regulation of the immune response

The immune-inflammatory response is associated with increased nitro-oxidative stress. The aim of this mechanistic review is to examine: (a) the role of redox-sensitive transcription factors and enzymes, ROS/RNS production, and the activity of cellular antioxidants in the activation and performance of macrophages, dendritic cells, neutrophils, T-cells, B-cells, and natural killer cells; (b) the involvement of high-density lipoprotein (HDL), apolipoprotein A1 (ApoA1), paraoxonase-1 (PON1), and oxidized phospholipids in regulating the immune response; and (c) the detrimental effects of hypernitrosylation and chronic nitro-oxidative stress on the immune response. The redox changes during immune-inflammatory responses are orchestrated by the actions of nuclear factor-κB, HIF1α, the mechanistic target of rapamycin, the phosphatidylinositol 3-kinase/protein kinase B signaling pathway, mitogen-activated protein kinases, 5' AMP-activated protein kinase, and peroxisome proliferator-activated receptor. The performance and survival of individual immune cells is under redox control and depends on intracellular and extracellular levels of ROS/RNS. They are heavily influenced by cellular antioxidants including the glutathione and thioredoxin systems, nuclear factor erythroid 2-related factor 2, and the HDL/ApoA1/PON1 complex. Chronic nitro-oxidative stress and hypernitrosylation inhibit the activity of those antioxidant systems, the tricarboxylic acid cycle, mitochondrial functions, and the metabolism of immune cells. In conclusion, redox-associated mechanisms modulate metabolic reprogramming of immune cells, macrophage and T helper cell polarization, phagocytosis, production of pro- versus anti-inflammatory cytokines, immune training and tolerance, chemotaxis, pathogen sensing, antiviral and antibacterial effects, Toll-like receptor activity, and endotoxin tolerance.

The role of L-arginine metabolism in neurocritical care patients

Nitric oxide is an important mediator of vascular autoregulation and is involved in pathophysiological changes after acute neurological disorders. Nitric oxide is generated by nitric oxide synthases from the amino acid L-arginine. L-arginine can also serve as a substrate for arginases or lead to the generation of dimethylarginines, asymmetric dimethylarginine, and symmetric dimethylarginine, by methylation. Asymmetric dimethylarginine is an endogenous inhibitor of nitric oxide synthase and can lead to endothelial dysfunction. This review discusses the role of L-arginine metabolism in patients suffering from acute and critical neurological disorders often requiring neuro-intensive care treatment. Conditions addressed in this review include intracerebral hemorrhage, aneurysmal subarachnoid hemorrhage, and traumatic brain injury. Recent therapeutic advances in the field are described including current randomized controlled trials for traumatic brain injuries and hemorrhagic stroke.

Thiol Modifications in the Extracellular Space-Key Proteins in Inflammation and Viral Infection

Posttranslational modifications (PTMs) allow to control molecular and cellular functions in response to specific signals and changes in the microenvironment of cells. They regulate structure, localization, stability, and function of proteins in a spatial and temporal manner. Among them, specific thiol modifications of cysteine (Cys) residues facilitate rapid signal transduction. In fact, Cys is unique because it contains the highly reactive thiol group that can undergo different reversible and irreversible modifications. Upon inflammation and changes in the cellular microenvironment, many extracellular soluble and membrane proteins undergo thiol modifications, particularly dithiol-disulfide exchange, S-glutathionylation, and S-nitrosylation. Among others, these thiol switches are essential for inflammatory signaling, regulation of gene expression, cytokine release, immunoglobulin function and isoform variation, and antigen presentation. Interestingly, also the redox state of bacterial and viral proteins depends on host cell-mediated redox reactions that are critical for invasion and infection. Here, we highlight mechanistic thiol switches in inflammatory pathways and infections including cholera, diphtheria, hepatitis, human immunodeficiency virus (HIV), influenza, and coronavirus disease 2019 (COVID-19).

The Breast Cancer Protooncogenes HER2, BRCA1 and BRCA2 and Their Regulation by the iNOS/NOS2 Axis

The expression of inducible nitric oxide synthase (iNOS; NOS2) and derived NO in various cancers was reported to exert pro- and anti-tumorigenic effects depending on the levels of expression and the tumor types. In humans, the breast cancer level of iNOS was reported to be overexpressed, to exhibit pro-tumorigenic activities, and to be of prognostic significance. Likewise, the expression of the oncogenes HER2, BRCA1, and BRCA2 has been associated with malignancy. The interrelationship between the expression of these protooncogenes and oncogenes and the expression of iNOS is not clear. We have hypothesized that there exist cross-talk signaling pathways between the breast cancer protooncogenes, the iNOS axis, and iNOS-mediated NO mutations of these protooncogenes into oncogenes. We review the molecular regulation of the expression of the protooncogenes in breast cancer and their interrelationships with iNOS expression and activities. In addition, we discuss the roles of iNOS, HER2, BRCA1/2, and NO metabolism in the pathophysiology of cancer stem cells. Bioinformatic analyses have been performed and have found suggested molecular alterations responsible for breast cancer aggressiveness. These include the association of BRCA1/2 mutations and HER2 amplifications with the dysregulation of the NOS pathway. We propose that future studies should be undertaken to investigate the regulatory mechanisms underlying the expression of iNOS and various breast cancer oncogenes, with the aim of identifying new therapeutic targets for the treatment of breast cancers that are refractory to current treatments.

Advances in Immunosuppressive Agents Based on Signal Pathway

Immune abnormality involves in various diseases, such as infection, allergic diseases, autoimmune diseases, as well as transplantation. Several signal pathways have been demonstrated to play a central role in the immune response, including JAK/STAT, NF-κB, PI3K/AKT-mTOR, MAPK, and Keap1/Nrf2/ARE pathway, in which multiple targets have been used to develop immunosuppressive agents. In recent years, varieties of immunosuppressive agents have been approved for clinical use, such as the JAK inhibitor tofacitinib and the mTOR inhibitor everolimus, which have shown good therapeutic effects. Additionally, many immunosuppressive agents are still in clinical trials or preclinical studies. In this review, we classified the immunosuppressive agents according to the immunopharmacological mechanisms, and summarized the phase of immunosuppressive agents.

The Role of Nitric Oxide in Stem Cell Biology

Nitric oxide (NO) is a gaseous biomolecule endogenously synthesized with an essential role in embryonic development and several physiological functions, such as regulating mitochondrial respiration and modulation of the immune response. The dual role of NO in embryonic stem cells (ESCs) has been previously reported, preserving pluripotency and cell survival or inducing differentiation with a dose-dependent pattern. In this line, high doses of NO have been used in vitro cultures to induce focused differentiation toward different cell lineages being a key molecule in the regenerative medicine field. Moreover, optimal conditions to promote pluripotency in vitro are essential for their use in advanced therapies. In this sense, the molecular mechanisms underlying stemness regulation by NO have been studied intensively over the current years. Recently, we have reported the role of low NO as a hypoxia-like inducer in pluripotent stem cells (PSCs), which supports using this molecule to maintain pluripotency under normoxic conditions. In this review, we stress the role of NO levels on stem cells (SCs) fate as a new approach for potential cell therapy strategies. Furthermore, we highlight the recent uses of NO in regenerative medicine due to their properties regulating SCs biology.

Superoxide Dismutase-3 Downregulates Laminin α5 Expression in Tumor Endothelial Cells via the Inhibition of Nuclear Factor Kappa B Signaling

The balance between laminin isoforms containing the α5 or the α4 chain in the endothelial basement membrane determines the site of leukocyte diapedesis under inflammatory conditions. Extracellular superoxide dismutase (SOD3) induces laminin α4 expression in tumor blood vessels, which is associated with enhanced intratumor T cell infiltration in primary human cancers. We show now that SOD3 overexpression in neoplastic and endothelial cells (ECs) reduces laminin α5 in tumor blood vessels. SOD3 represses the laminin α5 gene (LAMA5), but LAMA5 expression is not changed in SOD1-overexpressing cells. Transcriptomic analyses revealed SOD3 overexpression to change the transcription of 1682 genes in ECs, with the canonical and non-canonical NF-κB pathways as the major SOD3 targets. Indeed, SOD3 reduced the transcription of well-known NF-κB target genes as well as NF-κB-driven promoter activity in ECs stimulated with tumor necrosis factor (TNF)-α, an NF-κB signaling inducer. SOD3 inhibited the phosphorylation and degradation of IκBα (nuclear factor of the kappa light polypeptide gene enhancer in B-cells inhibitor alpha), an NF-κB inhibitor. Finally, TNF-α was found to be a transcriptional activator of LAMA5 but not of LAMA4; LAMA5 induction was prevented by SOD3. In conclusion, SOD3 is a major regulator of laminin balance in the basement membrane of tumor ECs, with potential implications for immune cell infiltration into tumors.

Hydropersulfides (RSSH) and Nitric Oxide (NO) Signaling: Possible Effects on S-Nitrosothiols (RS-NO)

S-Nitrosothiol (RS-NO) formation in proteins and peptides have been implicated as factors in the etiology of many diseases and as possible regulators of thiol protein function. They have also been proposed as possible storage forms of nitric oxide (NO). However, despite their proposed functions/roles, there appears to be little consensus regarding the physiological mechanisms of RS-NO formation and degradation. Hydropersulfides (RSSH) have recently been discovered as endogenously generated species with unique reactivity. One important reaction of RSSH is with RS-NO, which leads to the degradation of RS-NO as well as the release of NO. Thus, it can be speculated that RSSH can be a factor in the regulation of steady-state RS-NO levels, and therefore may be important in RS-NO (patho)physiology. Moreover, RSSH-mediated NO release from RS-NO may be a possible mechanism allowing RS-NO to serve as a storage form of NO.

The emerging roles of nitric oxide in ferroptosis and pyroptosis of tumor cells

Tumor cells can develop resistance to cell death which is divided into necrosis and programmed cell death (PCD). PCD, including apoptosis, autophagy, ferroptosis, pyroptosis, and necroptosis. Ferroptosis and pyroptosis, two new forms of cell death, have gradually been of interest to researchers. Boosting ferroptosis and pyroptosis of tumor cells could be a potential cancer therapy. Nitric oxide (NO) is a ubiquitous, lipophilic, highly diffusible, free-radical signaling molecule that plays various roles in tumorigenesis. In addition, NO also has regulatory mechanisms through S-nitrosylation that do not depend on the classic NO/sGC/cGMP signaling. The current tumor treatment strategy for NO is to promote cell death through promoting S-nitrosylation-induced apoptosis while multiple drawbacks dampen this tumor therapy. However, numerous studies have suggested that suppression of NO is perceived to active ferroptosis and pyroptosis, which could be a better anti-tumor treatment. In this review, ferroptosis and pyroptosis are described in detail. We summarize that NO influences ferroptosis and pyroptosis and infer that S-nitrosylation mediates ferroptosis- and pyroptosis-related signaling pathways. It could be a potential cancer therapy different from NO-induced apoptosis of tumor cells. Finally, the information shows the drugs that manipulate endogenous production and exogenous delivery of NO to modulate the levels of S-nitrosylation.

Pillars and Gaps of S-Nitrosylation-Dependent Epigenetic Regulation in Physiology and Cancer

Nitric oxide (NO) is a diffusible signaling molecule produced by three isoforms of nitric oxide synthase, which release NO during the metabolism of the amino acid arginine. NO participates in pathophysiological responses of many different tissues, inducing concentration-dependent effect. Indeed, while low NO levels generally have protective effects, higher NO concentrations induce cytotoxic/cytostatic actions. In recent years, evidences have been accumulated unveiling S-nitrosylation as a major NO-dependent post-translational mechanism ruling gene expression. S-nitrosylation is a reversible, highly regulated phenomenon in which NO reacts with one or few specific cysteine residues of target proteins generating S-nitrosothiols. By inducing this chemical modification, NO might exert epigenetic regulation through direct effects on both DNA and histones as well as through indirect actions affecting the functions of transcription factors and transcriptional co-regulators. In this light, S-nitrosylation may also impact on cancer cell gene expression programs. Indeed, it affects different cell pathways and functions ranging from the impairment of DNA damage repair to the modulation of the activity of signal transduction molecules, oncogenes, tumor suppressors, and chromatin remodelers. Nitrosylation is therefore a versatile tool by which NO might control gene expression programs in health and disease.

Human erythrocytes, nuclear factor kappaB (NFκB) and hydrogen sulfide (H2S) - from non-genomic to genomic research

Enucleated mature human erythrocytes possess NFĸBs and their upstream kinases. There is a negative correlation between eryptosis (cell death of erythrocytes) and the amount of NFĸB subunits p50 and Rel A (p65). This finding is based on the fact that young erythrocytes have the highest levels of NFĸBs and the lowest eryptosis rate, while in old erythrocytes the opposite ratio prevails. Human erythrocytes (hRBCs) effectively control the homeostasis of the cell membrane permeable anti-inflammatory signal molecule hydrogen sulfide (H2S). They endogenously produce H2S via both non-enzymic (glutathione-dependent) and enzymic processes (mercaptopyruvate sulfur transferase-dependent). They uptake H2S from diverse tissues and very effectively degrade H2S via methemoglobin (Hb-Fe3+)-catalyzed oxidation. Interestingly, a reciprocal correlation exists between the intensity of inflammatory diseases and endogenous levels of H2S. H2S deficiency has been observed in patients with diabetes, psoriasis, obesity, and chronic kidney disease (CKD). Furthermore, endogenous H2S deficiency results in impaired renal erythropoietin (EPO) production and EPO-dependent erythropoiesis. In general we can say: dynamic reciprocal interaction between tumor suppressor and oncoproteins, orchestrated and sequential activation of pro-inflammatory NFĸB heterodimers (RelA-p50) and the anti-inflammatory NFĸB-p50 homodimers for optimal inflammation response, appropriate generation, subsequent degradation of H2S etc., are prerequisites for a functioning cell and organism. Diseases arise when the fragile balance between different signaling pathways that keep each other in check is permanently disturbed. This work deals with the intact anti-inflammatory hRBCs and their role as guarantors to maintain the redox status in the physiological range, a basis for general health and well-being.

Understanding the role of S-nitrosylation/nitrosative stress in inflammation and the role of cellular denitrosylases in inflammation modulation: Implications in health and diseases

S-nitrosylation is a very fundamental post-translational modification of protein and non-protein thiols due the involvement of it in a variety of cellular processes including activation/inhibition of several ion channels such as ryanodine receptor in the cardiovascular system; blood vessel dilation; cGMP signaling and neurotransmission. S-nitrosothiol homeostasis in the cell is tightly regulated and perturbations in homeostasis result in an altered redox state leading to a plethora of disease conditions. However, the exact role of S-nitrosylated proteins and nitrosative stress metabolites in inflammation and in inflammation modulation is not well-reviewed. The cell utilizes its intricate defense mechanisms i.e. cellular denitrosylases such as Thioredoxin (Trx) and S-nitrosoglutathione reductase (GSNOR) systems to combat nitric oxide (NO) pathology which has also gained current attraction as novel anti-inflammatory molecules. This review attempts to provide state-of-the-art knowledge from past and present research on the mechanistic role of nitrosative stress intermediates (RNS, OONO^-, PSNO) in pulmonary and autoimmune diseases and how cellular denitrosylases particularly GSNOR and Trx via imparting opposing effects can modulate and reduce inflammation in several health and disease conditions. This review would also bring into notice the existing gaps in current research where denitrosylases can be utilized for ameliorating inflammation that would leave avenues for future therapeutic interventions.

Protein S-nitrosylation and oxidation contribute to protein misfolding in neurodegeneration

Neurodegenerative disorders like Alzheimer's disease and Parkinson's disease are characterized by progressive degeneration of synapses and neurons. Accumulation of misfolded/aggregated proteins represents a pathological hallmark of most neurodegenerative diseases, potentially contributing to synapse loss and neuronal damage. Emerging evidence suggests that misfolded proteins accumulate in the diseased brain at least in part as a consequence of excessively generated reactive oxygen species (ROS) and reactive nitrogen species (RNS). Mechanistically, not only disease-linked genetic mutations but also known risk factors for neurodegenerative diseases, such as aging and exposure to environmental toxins, can accelerate production of ROS/RNS, which contribute to protein misfolding - in many cases mimicking the effect of rare genetic mutations known to be linked to the disease. This review will focus on the role of RNS-dependent post-translational modifications, such as S-nitrosylation and tyrosine nitration, in protein misfolding and aggregation. Specifically, we will discuss molecular mechanisms whereby RNS disrupt the activity of the cellular protein quality control machinery, including molecular chaperones, autophagy/lysosomal pathways, and the ubiquitin-proteasome system (UPS). Because chronic accumulation of misfolded proteins can trigger mitochondrial dysfunction, synaptic damage, and neuronal demise, further characterization of RNS-mediated protein misfolding may establish these molecular events as therapeutic targets for intervention in neurodegenerative diseases.

Intrathecal and systemic alterations of L-arginine metabolism in patients after intracerebral hemorrhage

Alterations in the concentration of nitric oxide (NO) and L-arginine metabolites have been associated with the pathophysiology of different vascular diseases. Here, we describe striking changes in L-arginine metabolism after hemorrhagic stroke. Blood and cerebrospinal fluid (CSF) samples of patients with intracerebral hemorrhage (ICH) and/or intraventricular hemorrhage were collected over a ten-day period. Liquid chromatography-tandem mass spectrometry was used to quantify key substrates and products of L-arginine metabolizing enzymes as well as asymmetric (ADMA) and symmetric dimethylarginine (SDMA). Changes in the plasma were limited to early reductions in L-ornithine, L-lysine, and L-citrulline concentrations. Intrathecally, we observed signs of early NO synthase (NOS) upregulation followed by a decrease back to baseline accompanied by a rise in the level of its endogenous NOS-inhibitor ADMA. SDMA demonstrated increased levels throughout the observation period. For arginase, a pattern of persistently elevated activity was measured and arginine:glycine amidinotransferase (AGAT) appeared to be reduced in its activity at later time points. An early reduction in CSF L-arginine concentration was an independent risk factor for poor outcome. Together, these findings further elucidate pathophysiological mechanisms after ICH potentially involved in secondary brain injury and may reveal novel therapeutic targets.

Regulation of B cell functions by S-nitrosoglutathione in the EAE model

B cells play both protective and pathogenic roles in T cell-mediated autoimmune diseases by releasing regulatory vs. pathogenic cytokines. B cell-depleting therapy has been attempted in various autoimmune diseases but its efficacy varies and can even worsen symptoms due to depletion of B cells releasing regulatory cytokines along with B cells releasing pathogenic cytokines. Here, we report that S-nitrosoglutathione (GSNO) and GSNO-reductase (GSNOR) inhibitor N6022 drive upregulation of regulatory cytokine (IL-10) and downregulation of pathogenic effector cytokine (IL-6) in B cells and protected against the neuroinflammatory disease of experimental autoimmune encephalomyelitis (EAE). In human and mouse B cells, the GSNO/N6022-mediated regulation of IL-10 vs. IL-6 was not limited to regulatory B cells but also to a broad range of B cell subsets and antibody-secreting cells. Adoptive transfer of B cells from N6022 treated EAE mice or EAE mice deficient in the GSNOR gene also regulated T cell balance (Treg > Th17) and reduced clinical disease in the recipient EAE mice. The data presented here provide evidence of the role of GSNO in shifting B cell immune balance (IL-10 > IL-6) and the preclinical relevance of N6022, a first-in-class drug targeting GSNOR with proven human safety, as therapeutics for autoimmune disorders including multiple sclerosis.

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GSNO and GSNOR inhibitor (N6022) upregulates IL-10 and downregulates IL-6 in B cells.

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GSNO/N6022-mediated cytokine regulation occurs in a broad range of B cell subsets.

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GSNO/N6022 treatment ameliorates autoimmune disease of EAE.

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B cell transfer from N6022-treated or GSNOR null EAE mice to EAE mice shifts T cell balance (Treg > Th17) and alleviates EAE.

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The data provide the first insight into the therapeutic potential of GSNO/N6022 targeting B cells in multiple sclerosis.

Nitric Oxide and Electrophilic Cyclopentenone Prostaglandins in Redox signaling, Regulation of Cytoskeleton Dynamics and Intercellular Communication

Nitric oxide (NO) and electrophilic cyclopentenone prostaglandins (CyPG) are local mediators that modulate cellular response to oxidative stress in different pathophysiological processes. In particular, there is increasing evidence about their functional role during inflammation and immune responses. Although the mechanistic details about their relationship and functional interactions are still far from resolved, NO and CyPG share the ability to promote redox-based post-translational modification (PTM) of proteins that play key roles in cellular homeostasis, signal transduction and transcription. NO-induced S-nitrosylation and S-glutathionylation as well as cyclopentenone-mediated adduct formation, are a few of the main PTMs by which intra- and inter-cellular signaling are regulated. There is a growing body of evidence indicating that actin and actin-binding proteins are susceptible to covalent PTM by these agents. It is well known that the actin cytoskeleton is key for the establishment of interactions among leukocytes, endothelial and muscle cells, enabling cellular activation and migration. In this review we analyze the current knowledge about the actions exerted by NO and CyPG electrophilic lipids on the regulation of actin dynamics and cytoskeleton organization, and discuss some open questions regarding their functional relevance in the regulation of intercellular communication.

Role of protein S-Glutathionylation in cancer progression and development of resistance to anti-cancer drugs

The survival, functioning and proliferation of mammalian cells are highly dependent on the cellular response and adaptation to changes in their redox environment. Cancer cells often live in an altered redox environment due to aberrant neo-vasculature, metabolic reprogramming and dysregulated proliferation. Thus, redox adaptations are critical for their survival. Glutathione plays an essential role in maintaining redox homeostasis inside the cells by binding to redox-sensitive cysteine residues in proteins by a process called S-glutathionylation. S-Glutathionylation not only protects the labile cysteine residues from oxidation, but also serves as a sensor of redox status, and acts as a signal for stimulation of downstream processes and adaptive responses to ensure redox equilibrium. The present review aims to provide an updated overview of the role of the unique redox adaptations during carcinogenesis and cancer progression, focusing on their dependence on S-glutathionylation of specific redox-sensitive proteins involved in a wide range of processes including signalling, transcription, structural maintenance, mitochondrial functions, apoptosis and protein recycling. We also provide insights into the role of S-glutathionylation in the development of resistance to chemotherapy. Finally, we provide a strong rationale for the development of redox targeting drugs for treatment of refractory/resistant cancers.

bFGF alleviates diabetes-associated endothelial impairment by downregulating inflammation via S-nitrosylation pathway

Protein S-nitrosylation is a reversible protein modification implicated in both physiological and pathophysiological regulation of protein function. However, the relationship between dysregulated S-nitrosylation homeostasis and diabetic vascular complications remains incompletely understood. Here, we demonstrate that basic fibroblast growth factor (bFGF) is a key regulatory link between S-nitrosylation homeostasis and inflammation, and alleviated endothelial dysfunction and angiogenic defects in diabetes. Subjecting human umbilical vein endothelial cells (HUVECs) to hyperglycemia and hyperlipidemia significantly decreased endogenous S-nitrosylated proteins, including S-nitrosylation of inhibitor kappa B kinase β (IKKβ^C179) and transcription factor p65 (p65^C38), which was alleviated by bFGF co-treatment. Pretreatment with carboxy-PTIO (c-PTIO), a nitric oxide scavenger, abolished bFGF-mediated S-nitrosylation increase and endothelial protection. Meanwhile, nitrosylation-resistant IKKβ^C179S and p65^C38S mutants exacerbated endothelial dysfunction in db/db mice, and in cultured HUVECs subjected to hyperglycemia and hyperlipidemia. Mechanistically, bFGF-mediated increase of S-nitrosylated IKKβ and p65 was attributed to synergistic effects of increased endothelial nitric oxide synthase (eNOS) and thioredoxin (Trx) activity. Taken together, the endothelial protective effect of bFGF under hyperglycemia and hyperlipidemia can be partially attributed to its role in suppressing inflammation via the S-nitrosylation pathway.

eNOS-dependent S-nitrosylation of the NF-κB subunit p65 has neuroprotective effects

Cell death by glutamate excitotoxicity, mediated by N-methyl-D-aspartate (NMDA) receptors, negatively impacts brain function, including but not limited to hippocampal neurons. The NF-κB transcription factor (composed mainly of p65/p50 subunits) contributes to neuronal death in excitotoxicity, while its inhibition should improve cell survival. Using the biotin switch method, subcellular fractionation, immunofluorescence, and luciferase reporter assays, we found that NMDA-stimulated NF-κB activity selectively in hippocampal neurons, while endothelial nitric oxide synthase (eNOS), an enzyme expressed in neurons, is involved in the S-nitrosylation of p65 and consequent NF-κB inhibition in cerebrocortical, i.e., resistant neurons. The S-nitro proteomes of cortical and hippocampal neurons revealed that different biological processes are regulated by S-nitrosylation in susceptible and resistant neurons, bringing to light that protein S-nitrosylation is a ubiquitous post-translational modification, able to influence a variety of biological processes including the homeostatic inhibition of the NF-κB transcriptional activity in cortical neurons exposed to NMDA receptor overstimulation.

Substrate-specific recognition of IKKs mediated by USP16 facilitates autoimmune inflammation

The classic NF-κB pathway plays crucial roles in various immune responses and inflammatory diseases. Its key kinase, IKKβ, participates in a variety of pathological and physiological processes by selectively recognizing its downstream substrates, including p105, p65, and IκBα, but the specific mechanisms of these substrates are unclear. Hyperactivation of one of the substrates, p105, is closely related to the onset of inflammatory bowel disease (IBD) in Nfkb1-deficient mice. In this study, we found that IKKβ ubiquitination on lysine-238 was substantially increased during inflammation. Using mass spectrometry, we identified USP16 as an essential regulator of the IKKβ ubiquitination level that selectively affected p105 phosphorylation without directly affecting p65 or IκBα phosphorylation. Furthermore, USP16 was highly expressed in colon macrophages in patients with IBD, and myeloid-conditional USP16-knockout mice exhibited reduced IBD severity. Our study provides a new theoretical basis for IBD pathogenesis and targeted precision intervention therapy.

Redox Regulation, Oxidative Stress, and Inflammation in Group 3 Pulmonary Hypertension

Group 3 pulmonary hypertension (PH), which occurs secondary to hypoxia lung diseases, is one of the most common causes of PH worldwide and has a high unmet clinical need. A deeper understanding of the integrative pathological and adaptive molecular mechanisms within this group is required to inform the development of novel drug targets and effective treatments. The production of oxidants is increased in PH Group 3, and their pleiotropic roles include contributing to disease progression by promoting prolonged hypoxic pulmonary vasoconstriction and pathological pulmonary vascular remodeling, but also stimulating adaptation to pathological stress that limits the severity of this disease. Inflammation, which is increasingly being viewed as a key pathological feature of Group 3 PH, is subject to complex regulation by redox mechanisms and is exacerbated by, but also augments oxidative stress. In this review, we investigate aspects of this complex crosstalk between inflammation and oxidative stress in Group 3 PH, focusing on the redox-regulated transcription factor NF-κB and its upstream regulators toll-like receptor 4 and high mobility group box protein 1. Ultimately, we propose that the development of specific therapeutic interventions targeting redox-regulated signaling pathways related to inflammation could be explored as novel treatments for Group 3 PH.

Efficacy and safety of inhaled nebulized sodium nitrite in asthmatic patients

BACKGROUND

Nitrite is a physiologic nitric oxide (NO) derivative that can be bioactivated to NO. NO has been shown to attenuate airway inflammation and enhance the anti-inflammatory effect of corticosteroids in the animal model of asthma. Here, we aimed to investigate the efficacy and safety of inhaled sodium nitrite as add-on therapy with inhaled corticosteroid (ICS) in adult patients with persistent asthma.

METHODS

In protocol 1, 10 asthmatic patients were administered a single dose of nebulized 15-mg sodium nitrite to assess safety, effect on lung function, and pharmacokinetics of nitrite within 120 min. In protocol 2, 20 patients were randomly assigned to a nitrite (15 mg twice daily) group or a placebo group to assess the efficacy over 12 weeks. The primary outcome was the forced expiratory volume in 1 s (FEV₁). The secondary outcomes were other lung function parameters, unplanned asthma-related visits at the emergency department (ED) or outpatient department (OPD), admission days, asthma control test (ACT), and safety.

RESULTS

Nebulized sodium nitrite had neither acute adverse effect nor effect on lung function test within 120 min. No blood pressure change was seen. At week 12, FEV₁ increased in the nitrite group, whereas there was no change in the placebo group. There were 5 events of asthma exacerbation, 4 ED visits, and one unplanned OPD visit in the placebo group, but none of these was noted in the nitrite group. There was no change in ACT scores in both groups. No adverse event was reported during 12 weeks in the nitrite group. There was no change in methemoglobin levels and sputum inflammatory markers.

CONCLUSION

From our pilot trial, nebulized sodium nitrite is safe in asthmatic patients, and shows the potential to reduce asthma exacerbation compared with placebo.

Role of NO and S-nitrosylation in the Expression of Endothelial Adhesion Proteins That Regulate Leukocyte and Tumor Cell Adhesion

Leukocyte recruitment is one of the most important cellular responses to tissue damage. Leukocyte extravasation is exquisitely regulated by mechanisms of selective leukocyte-endothelium recognition through adhesion proteins in the endothelial cell surface that recognize specific integrins in the activated leukocytes. A similar mechanism is used by tumor cells during metastasis to extravasate and form a secondary tumor. Nitric oxide (NO) has been classically described as an anti-inflammatory molecule that inhibits leukocyte adhesion. However, the evidence available shows also a positive role of NO in leukocyte adhesion. These apparent discrepancies might be explained by the different NO concentrations reached during the inflammatory response, which are highly modulated by the expression of different nitric oxide synthases, along the inflammatory response and by changes in their subcellular locations.

Myeloperoxidase: A versatile mediator of endothelial dysfunction and therapeutic target during cardiovascular disease

Myeloperoxidase (MPO) is a prominent mammalian heme peroxidase and a fundamental component of the innate immune response against microbial pathogens. In recent times, MPO has received considerable attention as a key oxidative enzyme capable of impairing the bioactivity of nitric oxide (NO) and promoting endothelial dysfunction; a clinically relevant event that manifests throughout the development of inflammatory cardiovascular disease. Increasing evidence indicates that during cardiovascular disease, MPO is released intravascularly by activated leukocytes resulting in its transport and sequestration within the vascular endothelium. At this site, MPO catalyzes various oxidative reactions that are capable of promoting vascular inflammation and impairing NO bioactivity and endothelial function. In particular, MPO catalyzes the production of the potent oxidant hypochlorous acid (HOCl) and the catalytic consumption of NO via the enzyme's NO oxidase activity. An emerging paradigm is the ability of MPO to also influence endothelial function via non-catalytic, cytokine-like activities. In this review article we discuss the implications of our increasing knowledge of the versatility of MPO's actions as a mediator of cardiovascular disease and endothelial dysfunction for the development of new pharmacological agents capable of effectively combating MPO's pathogenic activities. More specifically, we will (i) discuss the various transport mechanisms by which MPO accumulates into the endothelium of inflamed or diseased arteries, (ii) detail the clinical and basic scientific evidence identifying MPO as a significant cause of endothelial dysfunction and cardiovascular disease, (iii) provide an up-to-date coverage on the different oxidative mechanisms by which MPO can impair endothelial function during cardiovascular disease including an evaluation of the contributions of MPO-catalyzed HOCl production and NO oxidation, and (iv) outline the novel non-enzymatic mechanisms of MPO and their potential contribution to endothelial dysfunction. Finally, we deliver a detailed appraisal of the different pharmacological strategies available for targeting the catalytic and non-catalytic modes-of-action of MPO in order to protect against endothelial dysfunction in cardiovascular disease.

Polysulfide and Hydrogen Sulfide Ameliorate Cisplatin-Induced Nephrotoxicity and Renal Inflammation through Persulfidating STAT3 and IKKβ

Cisplatin, a widely used chemotherapy for the treatment of various tumors, is clinically limited due to its extensive nephrotoxicity. Inflammatory response in tubular cells is a driving force for cisplatin-induced nephrotoxicity. The plant-derived agents are widely used to relieve cisplatin-induced renal dysfunction in preclinical studies. Polysulfide and hydrogen sulfide (H₂S) are ubiquitously expressed in garlic, and both of them are documented as potential agents for preventing and treating inflammatory disorders. This study was designed to determine whether polysulfide and H₂S could attenuate cisplatin nephrotoxicity through suppression of inflammatory factors. In renal proximal tubular cells, we found that sodium tetrasulfide (Na₂S₄), a polysulfide donor, and sodium hydrosulfide (NaHS) and GYY4137, two H₂S donors, ameliorated cisplatin-caused renal toxicity through suppression of the massive production of inflammatory cytokines, including tumor necrosis factor α (TNF-α), interleukin-1β (IL-1β), interleukin-6 (IL-6), and cyclooxygenase-2 (COX-2). Mechanistically, the anti-inflammatory actions of Na₂S₄ and H₂S may be mediated by persulfidation of signal transducer and activator of transcription 3 (STAT3) and inhibitor kappa B kinase β (IKKβ), followed by decreased phosphorylation of STAT3 and IKKβ. Moreover, the nuclear translocation of nuclear transcription factor kappa B (NF-κB), and phosphorylation and degradation of nuclear factor kappa B inhibitor protein alpha (IκBα) induced by cisplatin, were also mitigated by both polysulfide and H₂S. In mice, after treatment with polysulfide and H₂S donors, cisplatin-associated renal dysfunction was strikingly ameliorated, as evidenced by measurement of serum blood urea nitrogen (BUN) and creatinine levels, renal morphology, and the expression of renal inflammatory factors. Our present work suggests that polysulfide and H₂S could afford protection against cisplatin nephrotoxicity, possibly via persulfidating STAT3 and IKKβ and inhibiting NF-κB-mediated inflammatory cascade. Our results might shed light on the potential benefits of garlic-derived polysulfide and H₂S in chemotherapy-induced renal damage.

Physiopathology of nitric oxide in the oral environment and its biotechnological potential for new oral treatments: a literature review

OBJECTIVES

A narrative review on the NO properties and their relationship with the oral environment describing NO's molecular origin, role, and perspectives regarding oral pathological, physiological, and regenerative processes for future applications and possible use as prevention or treatment in dentistry.

MATERIALS AND METHODS

Pubmed was searched using the word "nitric oxide." Reviews, clinical studies, and experimental studies were eligible for the screening process. Similar search procedures were then performed with the additional search words "conservative dentistry," "orthodontics," "endodontics," "implants," "periodontics," "oral cancer," "pulp revascularization," and "oral surgery." Furthermore, references of included articles were examined to identify further relevant articles.

RESULTS

There is a relationship between NO production and oral diseases such as caries, periodontal diseases, pulp inflammation, apical periodontitis, oral cancer, with implants, and orthodontics. Studies on this relationship and uses of NO, in diagnosis, prevention, and treatment, are being developed. Also, some NO and oral cavity patents have already registered.

CONCLUSIONS

The understanding of how NO can interfere in oral health maintenance or disease processes can contribute to elucidate the disease development and optimize treatment approaches.

CLINICAL RELEVANCE

NO has considerable biotechnological potential and can contribute to improving diagnostics and treating the oral environment. As a biomarker, NO has an important role in the early diagnosis of diseases. Regarding treatments, NO can possibly be used as a regulator of inflammation, anti-biofilm action, replacing antibiotics, inducing apoptosis of cancerous cells, and contributing to the angiogenesis. All these studies are initial considerations regarding the relationship between NO and dentistry.

Nuclear Factor Kappa B Signaling Complexes in Acute Inflammation

Significance: Nuclear factor kappa B (NF-κB) is a master regulator of the inflammatory response and represents a key regulatory node in the complex inflammatory signaling network. In addition, selective NF-κB transcriptional activity on specific target genes occurs through the control of redox-sensitive NF-κB interactions. Recent Advances: The selective NF-κB response is mediated by redox-modulated NF-κB complexes with ribosomal protein S3 (RPS3), Pirin (PIR). cAMP response element-binding (CREB)-binding protein (CBP)/p300, peroxisome proliferator-activated receptor gamma coactivator 1 alpha (PGC-1α), activator protein-1 (AP-1), signal transducer and activator of transcription 3 (STAT3), early growth response protein 1 (EGR-1), and SP-1. NF-κB is cooperatively coactivated with AP-1, STAT3, EGR-1, and SP-1 during the inflammatory process, whereas NF-κB complexes with CBP/p300 and PGC-1α regulate the expression of antioxidant genes. PGC-1α may act as selective repressor of phospho-p65 toward interleukin-6 (IL-6) in acute inflammation. p65 and nuclear factor erythroid 2-related factor 2 (NRF2) compete for binding to coactivator CBP/p300 playing opposite roles in the regulation of inflammatory genes. S-nitrosylation or tyrosine nitration favors the recruitment of specific NF-κB subunits to κB sites. Critical Issues: NF-κB is a redox-sensitive transcription factor that forms specific signaling complexes to regulate selectively the expression of target genes in acute inflammation. Protein-protein interactions with coregulatory proteins, other transcription factors, and chromatin-remodeling proteins provide transcriptional specificity to NF-κB. Furthermore, different NF-κB subunits may form distinct redox-sensitive homo- and heterodimers with distinct affinities for κB sites. Future Directions: Further research is required to elucidate the whole NF-κB interactome to fully characterize the complex NF-κB signaling network in redox signaling, inflammation, and cancer.

Nitric Oxide Stimulates Acute Pancreatitis Pain via Activating the NF-κB Signaling Pathway and Inhibiting the Kappa Opioid Receptor

Pain is the most important clinical feature of acute pancreatitis (AP); however, its specific mechanism is currently unclear. In this study, we showed that AP caused an increase in nitric oxide (NO) secretion, activated the NF-κB pathway in the dorsal root ganglia (DRGs), and caused pain. We established an AP model in vivo and tested the expression of NO, the kappa opioid receptor (KOR), and pain factors. We showed that NO in AP was significantly elevated and increased the expression of pain factors. Next, by treating DRGs in vitro, it was found that NO activated the NF-κB pathway; conversely, NF-κB had no effect on NO. Moreover, inhibition of NF-κB promoted the KOR, whereas NF-κB did not change after KOR activation. Finally, behavioral experiments showed that a NO donor increased the pain behavior of mice, while a NO scavenger, NF-κB inhibitor, or KOR agonist attenuated the pain response in mice. These results suggest that iNOS/NO/NF-κB/KOR may be a key mechanism of pain in AP, providing a theoretical basis for the use of peripheral-restricted KOR agonists for pain treatment in AP.

Endogenous hydrogen sulfide sulfhydrates IKKβ at cysteine 179 to control pulmonary artery endothelial cell inflammation

BACKGROUND

Pulmonary artery endothelial cell (PAEC) inflammation is a critical event in the development of pulmonary arterial hypertension (PAH). However, the pathogenesis of PAEC inflammation remains unclear.

METHODS

Purified recombinant human inhibitor of κB kinase subunit β (IKKβ) protein, human PAECs and monocrotaline-induced pulmonary hypertensive rats were employed in the study. Site-directed mutagenesis, gene knockdown or overexpression were conducted to manipulate the expression or activity of a target protein.

RESULTS

We showed that hydrogen sulfide (H2S) inhibited IKKβ activation in the cell model of human PAEC inflammation induced by monocrotaline pyrrole-stimulation or knockdown of cystathionine γ-lyase (CSE), an H2S generating enzyme. Mechanistically, H2S was proved to inhibit IKKβ activity directly via sulfhydrating IKKβ at cysteinyl residue 179 (C179) in purified recombinant IKKβ protein in vitro, whereas thiol reductant dithiothreitol (DTT) reversed H2S-induced IKKβ inactivation. Furthermore, to demonstrate the significance of IKKβ sulfhydration by H2S in the development of PAEC inflammation, we mutated C179 to serine (C179S) in IKKβ. In purified IKKβ protein, C179S mutation of IKKβ abolished H2S-induced IKKβ sulfhydration and the subsequent IKKβ inactivation. In human PAECs, C179S mutation of IKKβ blocked H2S-inhibited IKKβ activation and PAEC inflammatory response. In pulmonary hypertensive rats, C179S mutation of IKKβ abolished the inhibitory effect of H2S on IKKβ activation and pulmonary vascular inflammation and remodeling.

CONCLUSION

Collectively, our in vivo and in vitro findings demonstrated, for the first time, that endogenous H2S directly inactivated IKKβ via sulfhydrating IKKβ at Cys179 to inhibit nuclear factor-κB (NF-κB) pathway activation and thereby control PAEC inflammation in PAH.